Voltage divider bias

108

01:25:55

Ie=Ic=1mA=0.001A
hfe=100
Ie and hfe can be found from multifunction meter

Vbe=0.7V
Vc=Vcc/2=10/2=5V
Rc=Vc/Ic=5/0.001=5000 ohm
Re=(from 0.1 to 0.5)Rc; 0.1*5000=500 ohm
Vbb>IeRe + Vbe=0.001*500+0.7=1.2; choose 1.5V
ree=26mV/Ie; ree=0.026/0.001=26 ohm
Rb=hfe((Vbb-Vbe)/Ie - ree - Re)=100((1.5-0.7)/0.001 - 26 - 500 =27,400 ohm

Will use Thevenin’s theorem to find R1 and R2
Rth=Rb; Vth=Vbb

R1=Rth*Vcc/Vth=27400*10/1.5=182,666.667 ohm
R2=1/(1/Rth-1/R1)=1/(1/27400-1/182666.667)=32,235.294 ohm

C=1/(2*pi*f*Xc); where f - lowest frequency, Xc reactance; Xc=0.1*Re or less

published 6 months ago

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